The present invention relates to periscopes and to 3 to 5 micron imaging systems for use in connection with military vehicles, such as tanks, armored personnel carriers, assault vehicles, amphibious craft, ships and gun boats.
The assignee of the present invention, Selectron, currently sells a commander periscope Model M-36, which provides dual adjacent optical channels, including a first visible optical channel and a second image-intensified optical channel. The system includes an upper housing in which a pivotable 35.degree. prism reflector is mounted for adjusting the elevation angle of the field of view. Using an elongated prism, there are provided side-by-side optical paths for the visible light optical channel and the image-intensified optical channel. The pivotable prism is mounted in the upper housing and is capable, by use of refraction, of viewing high elevation and low depression elevation angles as compared to mirror systems. Respective visible optical and image-intensified viewing systems are mounted in first and second lower housings, which are connected to the bottom of the upper housing for receiving light images therefrom.
In connection with enhancing night time or other low visibility capability of military vehicles it is desirable to provide imaging in the 3 to 5 micron spectral band in addition to visible and low light optical imaging. Infrared imaging may be provided as an alternate to image intensification.
A significant problem in providing infrared imaging in a unit which heretofore has accommodated only visible wavelength imaging is the fact that glass materials, used for prisms reflectors in known periscopes, are opaque to energy in the 3 to 5 micron in the spectral band. It is therefor an object of the present invention to provide a dual band periscope which provides side-by-side imaging of an optical field of view in the visible light spectral band and the 3 to 5 micron spectral band.